Genetic and morphometric variations of Mediterranean hake, Merluccius merluccius, in the Strait of Sicily (central Mediterranean): implications for stock assessment of shared resources

Allozyme, morphometric and growth analyses were applied to samples collected in the Strait of Sicily (central Mediterranean Sea) to test the hypothesis of the existence of a unique hake stock (Merluccius merluccius) in the study area. The level of genetic variation was detected from five polymorphic loci (ADH*, PGI-1; PGI-2*, PGM', SOD-1*). The average observed heterozygosity amounted to 0.421, while the average expected was 0.353. Weir & Cockerham statistics showed no heterogeneity, except for the single PGP locus (9 = 0.011; P < 0.05); the mean value was not significant (9 = 0.005; P > 0.05). Morphometric analyses revealed some differentiation. Females showed different relationships in six out of eight morphometric indices with total length, while the differences were significant for only four indices in males. Otolith readings also showed significant differences in growth rates of younger female specimens (age groups: 0-3 years) between the southwestern and northeastern parts of the Strait, whereas no clear variations were detected among males. These differences, conversely to genetic data, are probably related to the different environmental conditions characterizing the two sub-areas and give useful information for the management of this important resource.